The invention relates to an apparatus containing a heat exchange cell for utilizing waste heat of an air-cooled fuel cell. The invention also relates to a method of rendering utilizable the waste heat of a fuel cell (FC) battery containing a stack of fuel cells.
German Patent DE 44 42 285 C1 describes an air-cooled polymer electrolyte membrane (PEM) fuel cell which contains a negative terminal plate, a negative electrode, a membrane, a positive electrode and a positive terminal plate. The two terminal plates (or separator plates) are joined, in a mechanically fixed, gas-tight and electronically insulating manner, to the membrane via a frame element. To protect the membrane against drying out, the process gases supplied are at least partially humidified. To this end, the process gases are passed through a humidifier, e.g. a membrane humidifier, in which they are admixed with evaporated water.
In the case of liquid-cooled fuel cells, the humidifiers are perfused by the spent liquid coolant and are heated thereby. The extraction of heat from the cooling air, however, is more problematic, and so far no suitable heat exchangers exist which render the heat required for evaporation available from the spent cooling air. With the air-cooled fuel cell it has therefore been necessary, hitherto, for such energy of evaporation to be raised externally.
Published, Japanese Patent Application JP 61-243662 A discloses blockwise air cooling of a complete fuel cell stack by interposed stacks of heat exchangers. Additionally, Japanese Patent Application JP 10-284107 A describes a fuel cell stack containing heat exchangers that directly adjoin the stack. Finally, Published Japanese Patent Application JP 57-157470 A proposes cooling plates for use in a fuel cell stack, wherein the cooling plates are integrated into the fuel cell stack. In general, partitions are provided for this purpose in the heat exchangers.
It is accordingly an object of the invention to provide an apparatus and a method for utilizing the waste heat of an air-cooled fuel cell battery which overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, via which the waste heat of an air-cooled PEM fuel cell can be rendered utilizable with greater efficiency.
With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for utilizing a waste heat of an air-cooled fuel cell. The apparatus includes a heat exchange cell containing at least two plates being end plates or separator plates and a thermally conductive plate disposed in relation to the two plates to enclose a first chamber and a second chamber. During operation the first chamber receives a spent cooling air, and a humidifier membrane is disposed in the second chamber and subdivides the second chamber into a first subchamber and a second subchamber. During operation the first subchamber receives water and the second subchamber receives a process gas to be humidified.
In accordance with an added feature of invention, the heat exchange cell directly adjoins the air-cooled fuel cell.
In the invention, a humidifier through which the process gases or a process gas for the fuel cell battery are passed, is integrated into a heat exchange cell. In this configuration, each heat exchange cell is of such construction that the first separator plate together with the thermally conductive contact plate encloses a gas chamber in which the spent cooling air is ducted from the fuel cell stack, and a second separator plate together with the contact plate encloses a second chamber in which a humidifier membrane is disposed centrally. The humidifier membrane, together with the contact plate, defines the chamber in which the water for humidification is heated via the contact plate by where the waste heat of the fuel cell stack and, together with the separator plate, delimits the chamber in which the process gas to be humidified is ducted.
In the method according to the invention of rendering utilizable the waste heat of an air-cooled fuel cell battery, the spent cooling air is passed through a stack of heat exchange cells and in the process gives off its heat. It is advantageous for the heat exchange cell for utilizing the waste heat to adjoin the fuel cell battery directly, so that no heat will be lost via intermediate lines.
With the foregoing and other objects in view there is further provided, in accordance with the invention, a method of using utilizable waste heat of an air-cooled cell battery containing a stack of fuel cells. The method includes providing an apparatus for utilizing the waste heat of the air-cooled cell battery. The apparatus includes a stack of heat exchange cells, each of the heat exchange cells contains at least two plates selected being end plates or separator plates, a thermally conductive plate disposed in relation to the two plates to enclose a first chamber and a second chamber; and a humidifier membrane disposed in the second chamber and subdividing the second chamber into a first subchamber and a second subchamber. The first subchamber receives water and the second subchamber receives a process gas to be humidified. Spent cooling air is conducted through the first chamber of the heat exchange cells, the spent cooling air giving off its heat to the water and the process gas.
In accordance with another mode of the invention, there is the step of setting a number of the heat exchange cells in the heat exchange cell stack to be identical to a number of fuel cells in stack of fuel cells.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an apparatus and a method for utilizing the waste heat of an air-cooled fuel cell battery, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.